The invention relates to a method for keyframe-based displaying of a video presentation whilst enabling a user to select among said keyframes, and through such selecting, displaying a substantially continuous video stream based on said presentation, and which method displays various such keyframes in parallel in a reduced and static video format. The use of keyframes as representative parts of a video presentation that is recorded for subsequent selective playback has been proposed elsewhere. A continuous video stream means that video remains xe2x80x9conxe2x80x9d, which may include animation, a series of stills, or an interactive sequence of images. The character may be various, such as film, news, or for example a shopping list. State of the art is represented by the article xe2x80x98Content-Based Video Indexing and Retrievalxe2x80x99 by S. W. Smoliar and H. J. Zhang, IEEE Multimedia, Summer 1994, pages 62-72.
By themselves, keyframes may be derived from the video material upon its reception at the user""s premises through some derivation algorithm, or keyframes may be labelled as such by the video provider, for example, in that each new video shot will start with a keyframe. The present invention recognizes that such keyframes should be utilized so as to give users a dynamic overview over the presentation, combined with useful facilities for enabling them to edit the material in a sensible manner.
Therefore, amongst other things it is an object of the present invention to provide a user with an immediate feel of the dynamic aspects, as well as of the static content of the video presentation, as combined in a single video screen. Now, according to one of its aspects, the invention is characterized in that said displaying is controlled as starting from a particular active keyframe which subsequently to the selecting acts as a dynamic video cursor frame within said format. In this embodiment, the cursor frame moves in real time, thereby enabling users to discern between keyframes, that may have similar scene configurations but different dynamisms.
Advantageously, the method allows for rendering an audio-accompanied video presentation, whilst said rendering is controlled as starting from audio associated to a particular active keyframe that subsequently to the selecting acts as a discrete video cursor frame within said format. In certain presentations, for proper editing the audio is more discriminative than the video, and so the audio could represent the ongoing stream, while the video keyframe would operate as a kind of xe2x80x9cheaderxe2x80x9d pertaining to the interval between the two successive keyframes in question. The video keyframe may remain static, while the active keyframe that works as discrete or discretely stepping cursor frame may be highlighted in an appropriate manner.
Advantageously, said dynamic video cursor frame freezes upon coinciding with the next displayed keyframe""s content. The freezed display content may pertain either to the start, or to the end of the interval that has just been displayed. Subsequently, the next keyframe may become the a dynamic video cursor frame. The taking over may be controllable and/or programmable: this allows a user to view what editing the presentation will produce. Also, upon going to a next interval, the display mode may be altered, such as from normal to fast or slow display. The invention may be used for fully digital video, or rather for video in which the various video frames have digital labels for easy addressing.
Advantageously, the keyframes are set in a hierarchical structure and/or various keyframes are allowed to be deleted from display for so joining intervals of said presentation before and behind the deleted keyframe. In this way, fine-grained as well as coarse-grained editing can be applied in quick alternation. Again, the hierarchical structure may be implemented through the provider, or rather through some clustering algorithm. For example, if keyframes will be found through some cross-correlation, a rather small discrepancy therein may signal a low level keyframe, whereas a high discrepancy may signal a high level keyframe. The first could occur between successive shots in essentially the same movie scene, whereas the second would pertain to a changeover between scenes, that also may change overall conditions such as lighting level dramatically. Another situation is when various different types of video matter follow each other, such as news, film, or a service shop list. All this may facilitate the operations of the end user.
The invention also relates to a device for keyframe-based displaying of a video presentation and having selection means for enabling a user to select among said keyframes, and based on such selecting rendering a substantially continuous sensory stream relating to said presentation, said display device being arranged for displaying various such keyframes in parallel in a reduced and static video format, characterized in that the device has control means for controlling said rendering as starting from a particular active keyframe which subsequently acts as a video cursor frame within said format. The providing of the recited facilities in the environment of a user terminal, such as an enhanced video recorder plus TV set combination is believed to greatly extend user-directed performance thereof. Further advantageous aspects of the invention are recited in dependent claims.